Hydraulic operating mechanism for motor vehicle brakes



G. FARINA April 20, 1937.

HYDRAULIC OPERATING MECHANISM FOR MOTOR VEHICLE BRAKES Filed Oct. 20,1934 Y 2 v w 7 F mu v Q 1 w 7 I O o .m 2 J F ill.iliiillliltzn M. 7 7..HT 3 is 1 7 a @ifiiii 1 1 I H. m

Patented Apr. 20, 1937 HYDRAULIC OPERATING MECHANISM FOR MOTOR VEHICLEBRAKES Giovanni Farina, Turin, Italy Application October 20, 1934,Serial No. 749,265 In Italy October 23, 1933 3 Claims.

In vehicle brakes any accidental damage should be ascertained and ifpossible promptly repaired. In a hydraulic transmission for a brakeoperating mechanism small leakages can occur owing 5 to defectivepackings, which do not affect the braking efliciency provided theconduit is filled with liquid at the moment of braking.

This invention relates to improvements in hydraulic operating mechanismsfor vehicle brakes O and its object is to maintain a slight pressure inthe conduits even when the brakes are inoperative, in order to make upautomatically and promptly for any" small leakages that might takeplace. The user is enabled to ascertain the im- 5 portancepf'the leakageand to make a prompt repair.

According to this invention the liquid reservoir is provided with asmall pump submitted to the action of a spring which is stretchedperiodically, say every ten days or a fortnight, by the user of thevehicle. All the liquid filling the conduits is constantly under theaction of the spring weighted piston. The user of the vehicle judgesfrom the working of the pump piston 11 leakage of the conduits remainswithin the admissible limits. The expansion of the liquid is nothindered by the pump, of which the spring yields to the desired extentunder the increase in pressure on the liquid due to its expansion. 0 Themain cylinder of the brake is of valveless construction.

The accompanying drawing shows by way of example the object of thisinvention.

Figure 1 is a sectional view showing the reser- 5 voir and the maincylinder connected together.

Figure 2 shows on an enlarged scale a detail of the pump at thebeginning of its pumping stroke.

The main cylinder I is connected at one end 0 to the reservoir 2 by theconduit 3 on. which a manometric tube 5 can be branched, and at itsother end to the brake pipings by the conduit 4. In the drawing the maincylinder is shown in its inoperative position; its piston 6 is provided.5 with a packing l and its rod 8 is guided in the cylinder by a largecollar 9 provided with a packing II]. A long chamber Illa is formedbetween the packings l and Ill ahead of the piston and constantlycommunicates with the tube 3 of the 0 reservoir through the port [0. Thechamber la past the piston is connected with the tube 3 only in itsinoperative position by the port I which is covered as soon as thepiston moves further under the action of the brake pedal. The oppos- 5ing spring II is compressed between the cylinder bottom and the piston.No valve is provided on the cylinder, and the vent l2 serves only fordischarging air when the cylinder and piplngs are first filled withliquid.

The tube 3 does not open directly into the reservoir 2, but leads to thepump casing l3 integral with the reservoir with which it communicatesthrough the holes l3.

The piston H with its packing Ila is introduced through the upperopening of the casing l3 and its rod l5 threaded into the hub 0! pistonM, projects with its handle l5a through the cover of the reservoir. Thepiston 44 is pressed by a spring l6 under the action of which the holesl3 are kept covered by the piston, these holes working as inlet ports.The piston is provided with a valve I! provided with a packing l8, saidvalve opening during the suction stroke and closing during thecompression stroke. The spring is compressed by pulling the rod i5,whereby the holes H of the piston are brought opposite the holes l3 ofthe casing, so that the liquid flows through the holes l3, 14', H" andthe valve l'l into the pump casing l3, the tube 3, the main cylinder,the piping etc. which are thus filled. When the whole system has beenfilled evacuating the air through suitable vents that are closed afterfilling, the pump is released to the influence of spring I6 to place theliquid in the whole system under a slight pressure exerted by the spring16 which brings the holes H of the piston below the level of the holesii, the valve I'l remaining closed owing to the pressure of the liquidpast the same. Should any small leakage occur in the piping, this ismade up for by the liquid stored in the pump casing l3 under the valve11. Should an expansion of the liquid occur, this'produces through theport 1' of the cylinder an increase ln pressure against the piston Hwhich is raised compressing the spring 16, the liquid remaining in anycase under pressure.

The holes IS in the cylinder I3 are positioned in such manner that theyare uncovered by the piston to connect the reservoir directly with thebraking system if the pressure in the system exceeds a predeterminedvalue. N

When the brake pedal is operated, it displaces the piston 6 of the maincylinder through the lever l9, forcing the liquid in the chamber la intothe brake piping 4, thus covering the port I and establishing in thechamber 1a a pressure higher than that in the chamber lOa.

' When the pedal is released, the piston 6 moves back, establishing anunderpressure in the chamber lo and the liquid in the chamber lfla flowsunder the action of the spring I on the piston it or the pump it throughthe packing 1 into the chamber la before the latter is filled by theliquid returning from the brakes. The piston 6 uncovers at the end ofits stroke the port 1' through which the liquid excess can flowre-establishing the balance between the chambers la and Ila. The piston14 or the pump it shall thus have erformed a stroke to and tro withoutever causing the pressure in the piping to sink below that due to thespring is. As said above leakage is made up for as it occurs by theeffect of the downstroke of the piston H of the pump it. Every time theuser of the vehicle has an opportunity is to lift the engine and hood hemay ascertain the amount of liquid escaped by leakage by looking at thelength of the rod l8 projecting throughthe reservoir; this verificationwill be taciliated by providing the rod with reference marks. -Uni essleakage is abnormal, it will suiilce to act periodically upon the pump.2

"The constructive details of the 'maincylinder and reservoir may varyfrom the example described and shown in the drawing withoutideartingfrom the scope of this invention. 1

What I claim is: 1. In a hydraulic braking mechanism, the combinationwith a master control cylinder, a master piston in said master cylinderand a reservoir for supplying the fluid to said master cylinder, oi apump cylinder arranged in the reservoir and in communication with saidmaster cylinder in front 01 the master piston when said master piston isin non-operative position, said pump cylinder being provided with a portopening into the reservoir; a

spring-pressed pump piston in said pump cylinder, said pump pistonhaving an opening to provide communication between the reservoir andpump cylinder when said port and opening are in register, said pumppiston having-a bore therethrough from its upper to its lower side, anda iree' valve to close said bore when the pump piston is presseddownwardly and opening said bore when the piston is drawn upwardly.

2. In a hydraulic braking system, more particularly for motor vehicles,a feed tank, a pump cylinder having a circular row of ports providingconstant communication with said tank, a piston movable in said cylinderand controlling said ports, a spring acting on the piston to maintain apredetermined elastic pressure in the braking system and acheck valve insaid piston to prevent return of fluid from the braking system to thepump, said ports being situated in such manner that they are uncoveredby the piston to connect the tank directly with the braking system itthe pressure in the system exceeds a predetermined value.

8.- In a hydraulic braking system,- more particullrly for motorvehicles, a i'eed tank, a pump cylinder having a circular row oi portsproviding constant communication with said tank, a slide valve pistonmovable in said pump cylinder, said slide valve piston being providedwith a circular row 0! holes which in a position of the slide valvepiston register with the ports in the cylinder to permit passage of apredetermined quantiy of fluid from the tank into the space in thecylinder above the piston, a spring in said space acting on the slidevalve piston to maintain an elastic pressure in the braking system and aohmic valve in said slide valve piston to permit passage of the fluidfrom the pump into the braking system when the piston is lifted and toprevent passage in the opposite direction when the piston descends inthe cylinder, said holes being arranged in such manner that they areuncovered by the slide valve piston to directly connect the tank withthe braking system it the pressure in the latter excoeds a predeterminedvalue.

GIOVANNI FARINA.

